Electrical protective device.



B. H. SMITH.

ELECTRICAL PROTECTIVE DEVICE.

APPLICATION FILED MAY 4. ISIS.

1,231,659. Patented July 3,1917.

WITNESSES: INVENTOR UNITED STATES PATENT OFFICE.

BENJ MI H. SMITH, or rUn'rLEcnEEK,rnNnsYLvANIA, ASSIGNOB ro wss'rmc-HOUSE ELECTRIC AND MANUFACTURING COMPANY, a conronnrron or PENNSYL-VANIA.

ELECTRICAL PROTECTIVE DEVICE.

Specification of Letters Ilatent;

Patented ul 's, 1917.

To all whom it may concern:

Be it known that I, BENJAMIN H. SMITH, a citizen of the United States,and a resident of Turtle Creek, in the county of Allegheny and State ofPennsylvania, have invented a new and useful Improvement in ElectricalProtective Devices, of which the following is a specification.

My invention relates to electrical-protective devices and particularlyto relay mechanisms that are employed for tripping circuit interruptersor other similar devices upon the occurrence of predetermined circuitconditions.

My invention has for its object to provide a device of the aboveindicated character that shall operate correctly upon any value ofoverload.

My copendin application Serial No. 850,331, filed Jul 11, 1914,discloses a relay system that comprises a timeelement relay which isadapted to control an auxiliary Winding on a tripping electromagnet forthe purpose of permitting the electromagnet tooperate underpredetermined conditions. With a device of this type, a circuitinterrupter ma be tripped by current derived from the circuit inconnection with which it is employed without subjecting the contactmembers of the relay to any injurious arcing or welding. However, when adevice of this type is employed to interrupt very large currents, thetripping electromagnet will frequently operate irrespective of theauxiliary winding that is controlled by the relay. In other words, thetripping electromagnetfrequently operates before the relay functionsproperly.

In order to cause the tripping electromagnet to operate correctly forany value of current, I provide a main stationary magnetizable coremember having substantially the form of a hollow rectangle with anopening in one of its sides, an auxiliary stationary magnetizable memberof substantially E-shape and a movable core member having laterallyextending projections thereon that are disposed between the stationarycore members, and adapted to cooperate with the auxiliary stationarycore member under predetermined conditions and with the main stationarycore member under other predetermined. conditions. The main andauxiliary core members are adapted to be so separated by a relativelylarge air gap that, under normal conditions, the magnetic lines of forcefrom one of the core members will not traverse the other core ember. Themain and auxiliary. core mem e'rs are severally provided with a mainwinding that is adapted to be supplied with'current in accordance withthe current traversing the circuit to be protected. The main windingsare so connected as to normally tend to move the movable core member inopposite direct ons. The auxiliary core member is provided with anauxiliary winding that is adapted to be short circuited a time-intervalafter the occurrence of an overload upon the circuit to be protected.Thus, when the auxiliary winding on the auxiliary core member is shortcircuited, it neutralizes the effect of the main winding on theauxiliary core member and permits the movable core member to functionproperly.

The single figure of the accompanying drawing is a diagrammatic view ofa part of a system embodying my invention.

An alternating-current circuit 1 is provided with an interrupter 2 foropening it under predetermined conditions.- In order to trip the circuitinterrupter 2, I provide a relay system 3 that derives its energythrough a current transformer 4 and a voltage transformer 5.

The relay system 3 comprises a relay 6 that is of the induction type andpreferably constructed as set forth in Conrad Patent No. 1,137,840,issued May 4:, 1915, and a tripping electromagnet 7. The secondarywinding 8 of the transformer 5 is connected to windings 9 and 10 of therelay 6, and the secondary winding 11 of the transformer 4 is connectedin series relation to a winding 12 of'the relay 6 and windings 13 and 14of the tripping electromagnet 7. The relay 6 is provided with anarmature 15 that is mounted on ashaft 16 upon which a contact arm 17 isalso mounted. The contact arm 17 cooperates with a stationary contactmember 18 for the purpose of controlling the circuit of an auxiliary orcontrolling winding 19 of the tripping electromagnet 7 The trippingelectromagnet 7 comprises a main stationary magnetizable core member 20in the form of a hollow rectangle having a pole piece ll extendinginwardly and downwardly from its upper cross-piece and having a gap inits lower crossacre through which projects a movable core member 22 thatis adapted for longitudinal vertical movement. An auxiliary stationarymagnetizable core member 23 of substantially E-shape is disposed beneaththe main core member 20 and separated therefrom by an air ga 24. Themovable core member 22 is provided with laterally extending projections25 that are disposed in the air gap 24 and normally rest upon the outerand longer legs of the auxiliary core member 23. The movable core member22 is adapted to cooperate with both magnetizable core members 20 and 23and is surrounded by the windings 13, 14 and 19. The movable core member22 is provided with an operating rod 26 that is adapted to trip thelatch 27 of the circuit interrupter 2.

As hereinbefore stated, the windings 13 and 14 are supplied with currentfrom the secondary winding 11 of the transformer 4 and are preferablyconnected in series with the winding 12 of the relay 6, although theymay be connected in any other suitable relation with respect thereto.The winding 19 is normally open-circuited but is adapted to beclose-circuited by the engagement of contact members 17 and 18 of therelay 6 under predetermined circuit conditions, such, forinstance, asupon the occurrence of an overload or the reversal of the direction offlow of energy in the circuit 1.

Under normal c'ircuit conditions, the current in the winding 12 of therelay 6 is insufficient to cause the switch 1718 to close, and,consequently, the winding 19 remains open-circuited and is not affected.However, the windings 13 and 14 are continuously energized so long asthe circuit interrupter 2 remains closed, but, being adapted tocooperate with independent magnetic circuits, they exert opposing forcesupon the movable core member 22. The magnetic circuit of the winding 14being substantially closed under normal conditions, the movable coremember 22 remains stationary in the position shown. Also, since themagnetic circuit of the winding 14 is normally closed, whereas aconsiderable air gap exists in the magnetic circuit of the winding 13 atthe upper end of the movable core member 22, it is obvious that thewinding 14 may, and preferably does, have a smaller number ofconvolutions than the winding 13.

When an overload or other abnormal condition occurs upon the circuit 1.an increased current is induced in the winding 11 of the transformer 4that is sufficient to cause the relay 6 to close the switch 17-18 theclosing of which may be delayed or not, as desired. When the switch1'7-18 is closed, the winding 19 is close-circuited and an electromotiveforce is induced by it in the winding 14, thereby decreasing themagnetizing effect of the winding 14 because of the counter-fluxproduced by the winding 19. When the magnetizing efl'ect of the winding14 is reduced, the pull exerted by the winding 13 is permitted topredominate over that of the winding 14, and the movable core member 22will rise in its entirety, thereby tripping the circuit interrupter 2.When the overload or other abnormal circuit condition disappears or thecircuit interrupter is closed, the switch 17-18 is opened, and themovable core member 22 is returned by gravity to its normal position.

The auxiliary stationary core member is disposed such a distance fromthe main core member 20 that the winding 13 will normally not have anyefi'ect upon the projections 25 of the movable core member 22, and theprojections 25 and the auxiliary core member 23 are of such dimensionsthat, under shortcircuit conditions in the circuit 1, they will notbecome saturated before the stationary core member 20. Thus, no matterwhat load traverses the circuit 1, the movable core member 22 will notbe moved upwardly until the relay 6 has functioned.

An adjusting screw 28 is provided for adjusting the position of avspring 29 that is disposed in an opening 30 in the shorter leg of thestationary core member 23. By adjusting the position of the spring, theamount of efi'ecti e Weight of the movable core member 22 may be sovaried that the device can be set to operate at any predeterminedminimum value of operating current.

While I have shown and described my invention in the preferred form itmay obviously be variously modified within the scope of the appendedclaims.

I claim as my invention:

1. An electromagnetic device comprising two stationary magnetizable coremembers separated by an air gap, a common movable core member therefor,a winding for each of the stationary core members normally tending tomove the movable core member in opposite directions, and an auxiliarywinding for neutralizing the efiect of one of the windings.

2. An electromagnet comprising a main magnetizable core member havingsubstantially the foam of a hollow rectangle having an opening in one ofits sides, an armature extending through the opening and having anenlarged portion intermediate its ends, and an auxiliary core memberhaving legs that are adapted to engage the enlarged portion of the saidarmature.

3. An electromagnet comprising a main magnetizable core member havingsubstantially the form of a hollow rectangle having an opening in one ofits sides, an armature extending through the opening and having anenlarged portion intermediate its ends, and an auxiliary core member ofsubstantially E-shape the outer legs of which are adapted to normallyengage the enlarged portion of the said armature.

4. An electromagnetic device comprising a main stationary magnetizablecore member, a movable core member having an enlarged portionintermediate its ends and an auxiliary stationary magnetizable coremember having legs that are adapted to normally engage the enlargedportion of the movable core member.

5. An electromagnetic device comprising a main stationary magnetizablecore mem her having substantially the form of a 1101- low rectanglehaving an opening in one of its sides, a movable core member extendingthrough the opening and having laterally extending portions thereon, andan auxiliary magnetizable core member having legs terminating adjacentthe laterally extending portions of the movable core member.

6. An electromagnetic device comprising a main stationary magnetizablecore member having substantially the form of a hollow rectangle havingan opening in one of its sides, a movable core member extending throughthe opening and having laterally extending portions thereon, and anauxiliary magnetizable core member of a substantially E-shape the outerlegs of which are adapted to normally engage the laterally extendingportion and the central leg of which is adapted to normally engage oneend of the movable core member.

7. An electromagnetic device comprising two stationary magnetizablemembers, and a common movable core member therefor having laterallyextending projections thereon that are disposed between the stationarymagnetizable members, said laterally extending projections being adaptedto normally coiiperate with only one stationary magnetizable member.

8. An electromagnetic device comprising two stationary magnetizable coremembers, and a common movable core member therefor having laterallyextending projections thereon disposed between the two core mem bers,said laterally extending projections being adapted to cooperate with onecore member under predetermined conditions and with the other underother predetermined conditions.

In testimony whereof, I have hereunto subscribed my name this 29th dayof April 1916.

BENJAMIN H. SMITH.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents, Washington, D. G.

